Petroleum hydrocarbon compositions

ABSTRACT

AN ADDITIVE HAVING DETERGENCY AND LUBRICITY PROPERTIES FOR INCORPORATION IN PETROLEUM HYDROCARBON AND PETROLEUM HYDROCARBON COMOSITIONS CONATINING SAID ADDITIVE. THE ADDITIVE IS THE CONDENSATION PRODUCT OF A POLYETHERPOLYESTER POLYOL CONTAINING FROM 2 TO ABOUT 12 HYDROXYL GROUPS AND A MONOCARBOXYLIC ACID WHEREIN ABOUT 85100% OF THE HYDROXYL GROUPS OF THE POLYOL ARE ESTERIFIED BY CONDENSATION WITH THE MONOCARBOXYLIC ACID. THE ADDITIVE IS GENERALLY INCORPORATED IN HYDROCARBON FUELS AND HYDROCARBON LUBRICATING OILS, BUT ITS GREATEST UTILITY IS IN HYDROCARBON LUBRICATING OILS. THE PREFERRED LUBRICATING OIL COMPOSITION IS A 2-CYCLE ENGINE OIL COMPROSING A MAJOR PROPORTION OF A HYDROCABON LUBRICATNG OIL AND A MINOR PROPORTION OF THE ADDITIVE OF THE INVENTION.

US. Cl. 260-22 R 7 Claims ABSTRACT OF THE DISCLOSURE An additive having detergency and lubricity properties for incorporation in petroleum hydrocarbon and petroleum hydrocarbon compositions containing said additive. The additive is the condensation product of a polyetherpolyester polyol containing from 2 to about 12 hydroxyl groups and a monocarboxylic acid wherein about 85- 100% of the hydroxyl groups of the polyol are esterified by condensation with the monocarboxylic acid. The additive is generally incorporated in hydrocarbon fuels and hydrocarbon lubricating oils, but its greatest utility is in hydrocarbon lubricating oils. The preferred lubricating oil composition is a 2-cycle engine oil comprising a major proportion of a hydrocarbon lubricating oil and a minor proportion of the additive of this invention.

BACKGROUND OF THE INVENTION Petroleum hydrocarbon products often require the addition thereto of various additives to improve various properties. There is often a need, for example, to impart carburetor detergency and upper cylinder lubricating properties to a gasoline composition. Also, there is often a need to impart detergency properties and to enhance the lubricity of a lubricating oil composition. The need for detergency arises from the necessity to keep engine parts free from varnish and sludge build-up as well as the need to keep combustion products and sludge in suspension in the oil.

The foregoing is especially true in the case of 2-cycle engine operation where the lubricating oil is mixed with the fuel. The main requirement is to keep the pistons and rings free from deposits, the principal cause of which is incomplete combustion of the fuel/oil mixture to form deposit precursors. The deposit precursors then polymerize to resins which form varnish and sludge.

Another type of deposit build-up in 2-cycle engines is the accumulation of carbon deposits in the exhaust ports or the muffler system. Such deposit build-up results in back pressure which causes power loss, particularly With smaller engines. Therefore, the residue from the combustion of the oil, which is burned with the fuel in the combustion chamber, should be in the form of a friable ash which does not build up in critical areas.

Still another type of deposit build-up is the formation of a whisker of lead salts across the electrode gap of the spark plug. This necessitates frequent plug removal and cleaning.

The mechanism for deposit control due to the presence of a detergent, or dispersant, in the lubricating oil is postulated to be similar in 2-cycle and 4-cycle engines. The detergent is adsorbed on the carbonyl and carboxyl groups of the droplets of deposit precursors and resins to form a protective film which prevents these droplets from agglomerating into varnish and sludge. These detergents also keep the deposit precursors and resins suspended in the air/fuel mixture within the combustion chamber for more complete burning or to exit with the gases at the exhaust ports. In addition, the detergent present in the crankcase oil of 4-cycle engines keeps combustion products and sludge in suspension in the oil to thereby prevent sludge build-up in the crankcase.

United States Patent 'ice It is proposed that the ability of detergent additives to surround deposit precursors and resin droplets is a function of the detergents ability to plate out on the surface of the metal where it acts as a lubricant in its own right, thus enhancing the lubricity of the oil composition.

It is well known that the frictional properties of oils are related to the rate of chemical and/or physical adsorption, the number of layers adsorbed, and the strength of the adsorbed film. Thus there is an apparent relationship between frictional properties of engine oils and engine cleanliness, i.e., the higher the degree of lubricity of the oil, the cleaner the engine. Therefore, the lubricity due to an additive of this invention is a function of its dispersant power. Accordingly, by meaursing the lubricity of an oil composition containing a detergent additive, a measure of the additives dispersing power is obtained.

It is a desirable feature of the lubricating oil additives that they be thermally stable in view of the elevated temperatures to which they are subjected. This is particularly true in the case of 2-cycle engine oils where the oil is mixed with and burned with the fuel.

SUMMARY It is an object of this invention to provide an additive for hydrocarbon petroleum products having detergency properties.

It is another object of this invention to provide an ashless additive for petroleum hydrocarbon products having, in addition to detergency properties, thermal stability and lubricity characteristics as well as rust inhibitory properties.

It is yet another object of this invention to provide hydrocarbon petroleum compositions having improved detergency and lubricity characteristics.

Still another object of this invention is to provide a lubricating oil composition having, in addition to improved detergency properties, enhanced lubricity and thermal stability as well as rust inhibitory characteristics.

Other objects and advantages of this invention will be apparent to those skilled in the art from this disclosure.

The foregoing objects are achieved in accordance with this invention. In general, this invention consists of an additive for petroleum hydrocarbon products comprising the condensation product of a polyether-polyester polyol having 2 to about 12 hydroxyl groups and a mono-- carboxylic acid wherein at least about of the hydroxyl groups of said polyol are converted to ester groups by condensation with said monocarboxylic acid; and a petroleum hydrocarbon composition comprising a major proportion of a petroleum hydrocarbon and a minor proportion of the additive of this invention.

Thus by practicing the instant invention, an ashless detergency additive for petroleum hydrocarbon products is obtained. The additive has, in addition to detergency properties, thermal stability and lubricity characteristics as well as rust inhibitory properties. Petroleum hydrocarbon compositions, particularly hydrocarbon lubricating oil compositions, containing the additive of this invention exhibit thermal stability and rust inhibitory properties as well as increased lubricity and detergency characteristics. In addition, engines lubricated by hydrocarbon lubricating oil compositions of this invention are characterized by enhanced cleanliness.

DESCRIPTION OF THE PREFERRED EMBODIMENTS This invention is concerned with ashless detergency additives for petroleum hydrocarbon products and petroleum hydrocarbon product compositions containing said additives. The additives of this invention impart to petroleum hydrocarbon products superior detergency properties as well as enhanced lubricity. Petroleum hydrocarbon compositions of this invention are also characterized by improved thermal stability as Well as enhanced rust inhibitory properties. While the additives of this invention may be used in petroleum hydrocarbon products generally, they are particularly useful in gasoline and hydrocarbon lubricating oils, especially 2-cycle engine oils. Engines lubricated with the hydrocarbon lubricating oil compositions of this invention exhibit enhanced cleanliness.

The detergency additive of this invention broadly comprises the condensation product of a polyether-polyester polyol having 2 to about 12 hydroxyl groups and a monocarboxylic acid wherein at least about 85% of the hydroxyl group of said polyol are converted to ester groups by condensation with said monocarboxylic acid.

The polyether-polyester polyol is a hydroxyl-terminated polymer which comprises chains containing both ether and ester linkages. Such polyols are described in US. Pat. 3,455,886. The polyols are characterized in that the sequence of ester and ether units in the polymer chain is ordered. For example, a typical chain of the polyetherpolyester polyol may be represented by:

O O A-("J-R-ii-O-IV-OR-OROH where R represents the residue of an anhydride of a polybasic organic acid, R represents the residue of a cyclic ether, and A represents a structure grouping contained in a polymerization starter molecule.

While the polyether-polyester polyols are described in detail in US. Pat. 3,455,886, broadly the polyols are characterized by having at least two, and preferably two to about twelve, hydroxyl groups, a relatively low viscosity at room temperature, and a narrow molecular weight distribution. In general, they have an equivalent weight of from about 80 to 300, and a hydroxyl number of from 187 to 700.

These hydroxyl-terminated polymers containing both ether and ester linkages are produced by reacting an anhydride of an organic polycarboxylic acid with a suitable polymerization starter compound containing at least two groups selected from the group consisting of alcoholic hydroxyls, primary amines, secondary amines, and combinations thereof, to form a partial ester or partial amide, substantially free of unreacted anhydride. This intermediate reaction product is then reacted with an excess, based on the amount of anhydride reacted, of a cyclic ether containing at least one heterocyclic ring comprising 1 ethereal oxygen and at least 2 carbons to form the polyol.

More particularly, the polymerization starter and anhydride reactants are reacted in amounts such that the ratio of equivalents of anhydride to equivalents of starter is from about 0.1 to about 2.0. The conditions of this first stage reaction are such that all or substantially all of the anhydride reacts with the hydroxyl or amine groups of the starter leading to the formation of a partial ester or partial amide and generating carboxyl groups. This intermediate reaction product is then caused to react with a cyclic ether in an amount of from about 1.5 to about 14 equivalents per equivalent of anhydride employed in the first stage reaction to form the polyether-polyester polyol.

The polyether-polyester polyol is described in detail in US. Pat. 3,455,886. In the patent, the various components used to prepare the polyol, i.e., the starter compound, the polycarboxylic acid anhydride, and the cyclic ether, are described and numerous examples given. Also described are the ratios of starter compound, acid anhydride, and cyclic ether as well as reaction conditions for formation of the polyol. The properties of the polyol are also given. It has been found for the purposes of the instant invention that the preferred polyether-polyester polyol is prepared using glycerol as the starter compound, phthalic anhydride as the polycarboxylic acid anhydride,

and propylene oxide as the cyclic ether. The resultant polyol contains 3 hydroxyl groups and has a preferred equivalent weight of about 130.

The monocarboxylic acid broadly contains about 8 to 30 carbons and preferably about 12 to 24 carbons. The monocarboxylic acid may be an aliphatic acid, preferably a branched chain aliphatic acid; an aromatic acid containing a branched aliphatic chain having at least 12 carbons on the aromatic ring; or a naphthenic acid containing a branched aliphatic chain having at least 12 carbons on the naphthenic ring. The preferred class of monocarboXylic acids are the branched chain aliphatic acid containing about 8 to 30, and preferably about 12 to 24, carbons. Examples of suitable monocarboxylic acids are S-methylheptanoic acid, Z-ethylhexanoic acid, 9-ethyldodecanoic acid, phenylstearic acid, l8-butyleicosoic acid, 8-ethyldecanoic acid, p-isostearyl benzoic acid, 4-isododecyl-l-cyclohexanoic acid, 4-( l7-ethyloctadecyl)-1-naphthoic acid, 1-isododecyl-5-carboxycyclooctane, tallow fatty acid such as Emery 500 Fatty Acid, and mixtures thereof. The preferred monocarboxylic acid is isostearic acid.

The ratio of monocarboxylic acid to the polyetherpolyester polyol is such as to convert about to of the hydroxyl groups of the polyol to ester groups by condensation with the monocarboxylic acid. In the case where the additive is the condensation product of isostearic acid and a polyether-polyester polyol prepared from glycerol, phthalic anhydride, and propylene oxide, it is preferred that about 100% of the hydroxyl groups of the polyol be converted to ester groups by condensation with the isostearic acid.

The petroleum hydrocarbon compositions of our invention broadly comprise a major proportion of a petroleum hydrocarbon product and a minor proportion of the inventive additive. Generally, the petroleum hydrocarbon compositions contain about 1 to 20% by volume, based on the hydrocarbon composition, of the additive of this invention. It is preferred that the petroleum hydrocarbon composition contain about 3 to 15% by volume, based on the petroleum hydrocarbon composition, of the additive.

The additives of the instant invention are useful in petroleum hydrocarbon products generally. However, it is contemplated that the additives will have their greatest utility in gasoline and in hydrocarbon engine oils, particularly in 2-cycle engine oils. The detergency additives of this invention will find utility in gasoline as carburetor detergency additives and as upper cylinder lubricants. It is anticipated that the detergency additives of this invention will be most useful in hydrocarbon engine oils, especially 2-cycle engine oils, to produce hydrocarbon lubricating oil compositions having enhanced detergency and lubricity characteristics as Well as thermal stability and rust inhibitory properties.

Our invention will be further illustrated by the following specific examples.

Example I To a 500 ml. round bottom flask fitted with magnetic stirrer, thermometer, Dean-Stark trap, condenser, and nitrogen-inlet tube are added 77.2 g. (0.6 eq.) of a polyether-polyester polyol having an equivalent weight of and which is prepared using glycerol as the starter anhydride, and propylene oxide as the cyclic ether. Also compound, phthalic anhydride as the polycarboxylic acid added to the flask are 185.4 g. (0.6 eq.) of Emery 871 isostearic acid and 100 ml. of xylene. The stirred reaction mixture is heated under reflux for about 72 hours While nitrogen is slowly purged through the system. At the end of this time 10 ml. of Water of condensation, 92.6% of the theoretical amount for ester formation, are collected in the Dean-Stark trap. The xylene is removed by distillation under reduced pressure at a temperature of 100-160 C. to leave a residue of 252 g. of a light yellow, free flowing liquid. Infrared spectroscopy shows the product to be essentially free of absorptions due to the presence of hydroxyl and carboxyl functionalities while absorption at 1740 cm.- shows the presence of ester carbonyl groups. The product has an acid number of 15.6 mg. KOH/g. indicating the presence of some unreacted acid. The solubility of the product in base hydrocarbon oil is greater than 10 volume percent.

As mentioned above, the eifectiveness of the additives of this invention as dispersants in lubricating oil compositions is indicated by and is a function of the lubricity imparted to the oil composition by said additives. From friction data, the Lubricity Index (LI at six different temperatures is determined. The Normal Lubricity Index (NLI) is the average of the Lubricity Indexes at the six temperatures. The Lubricity Index is determined from the expression:

a b b d D wherein the lower case letters are for frictional values of a standard oil composition and the upper case letters are the corresponding frictional values for an oil composition containing the experimental additive of this invention.

a=static coefficient of friction b=coeflicient of friction at 2 f.p.m. b =coefiicient of friction at 50 f.p.m. d=coefficient of slip-stick or static coeflicient of friction coefficient of friction at 2 f.p.m.

d'=ratio of coefficient of friction at 10 f.p.m. to coefficient of friction at 100 f.p.m. LI =Lubricity Index at T F.

NLI LIIOO L50 zoo 250 aoo sso From the foregoing it can be seen that if an oil composition containing an additive of this invention is equal in lubricity to the standard oil composition at a given temperature T, it will have a value for LI of 100. A value for LI less than 100 indicates poorer lubricity than the standard and a value for LI greater than 100 indicates better lubricity than the standard at temperature T. The same holds true for Normal Lubricity Index (NLI) which is an average of the Lubricity Indexes at the 6 dilferent temperatures. Thus if an oil composition containing an additive of this invention has a NLI value greater than 100, it will have greater lubricity than the standard oil composition and hence it will have better dispersant power.

The friction data are obtained by using the friction apparatus and procedure described by Hain in a paper entitled Performance of Oil Additives. The paper was presented at Session C of a convention of the American Society of Lubrication Engineers at Chicago, Ill. on May 28, 1964.

The friction apparatus is essentially a modified drill press containing a temperature recorder, a variable speed motor, and a single channel strain gauge to measure coefficient of friction. The friction couple used in these experiments is blotter paper vs. polished, cold rolled steel. The blotter paper is chosen because of its consistent porosity and surface roughness. The consistent porosity insures uniform results from day to day.

A 2-cycle engine oil composition is prepared containing 10 volume percent of the inventive additive for which the preparation is described above. The standard oil composition, which by definition has a NLI of 100, is a Z-cycle engine oil composition containing 10 volume percent of a commercially available additive. The 2-cycle engine oil composition containing the additive 0f the invention is found to have a NLI of 121 while a base 2-cycle engine oil containing no additive has a NLI of 91.

Since, as pointed out above, an increase in the lubricity of a 2-cycle engine oil results in improved engine cleanliness, a 2-cycle engine operating on a fuel/oil mixture in which the oil contains the lubricity-improving additive of this invention will operate cleaner with less deposit buildup than it will on a similar fuel/oil mixture in which the oil contains either no additive or contains the commercially available additive.

Example II A number of lubricating oil compositions are prepared containing various concentrations of the inventive additive of Example I. The interfacial tension (IFT) between each lubricating oil composition and water is compared to that between a base lubricating oil containing no additive and water. The percent reduction in IFT is determined from the expression:

TABLE I Additive concentration,

vol. percent: Percent IFT reduction The data in Table I illustrate the reduction in IFT of lubricating oil compositions containing the additives of this invention in comparison to the base oil. There is evidence that IFT is a measure of the detergency activity of an oil and that additives which produce a large percent reduction in IFT also exhibit detergency properties.

Example III The termal and oxidative stabilities of a lubricating oil composition containing an additive of this invention are determined. A 15 ml. sample of a lubricating oil composition containing 10 volume percent of the additive of Example I is heated in a test tube at 375 F. for 10' days. The hot solution is then decanted. The test tube is allowed to drain and is examined for sludge deposits. A lubricating oil composition containing 10 volume percent of a commerically available additive is similarly tested as a comparison. No oil-insoluble sludge is found in either oil composition at the conclusion of the test. Base oil alone similarly tested gave sludge formation.

Example IV A lubricating oil composition containing 10 volume percent of the inventive additive of Example I and a base hydrocarbon lubricating oil containing no additive are subjected to the Shell Four Ball Wear test. The test involves placing three stationary steel balls in triangular configuration in a cup containing the oil composition to be tested while a fourth ball which is rotatable and capable of having a load applied thereto is brought into contact with the three stationary balls in such a Way as to form a tetrahedron. The conditions of the test are to rotate the fourth ball at 1800 r.p.m. at a temperature of F. for 1 hour. The test is run under a load of 7.5 kg. At the end of the test, the wear, i.e., the average of the scar diameters of the three stationary balls, is determined. The greater the wear, the poorer the lubricity of the oil composition. The results of the test are shown in Table II.

TABLE II Additive concentration in the lubrieating oil composition, Wear Additive vol. percent mm.

0. 47 Additive of Example L 0.

From Table II it is seen that the oil composition containing the inventive additive of Example I permits less wear than does the base hydrocarbon oil containing no additive.

Example V A lubricating oil composition containing 10 volume percent of the inventive additive of Example I and the base hydrocarbon oil containing no additive are subjected to the ASTM D 665-A rust test. The steel test piece from the oil composition containing the inventive additive has no rust. In contrast, the steel test piece from the base oil is severely rusted. This illustrates that the additive of this invention is effective in imparting rust inhibitory properties to hydrocarbon lubricating oils.

Example VI An additive according to this invention is prepared by following the procedure described in Example I wherein 0.3 eq. of phenylstearic acid and 0.3 eq. of the polyetherpolyester polyol described in Example I are condensed. Infrared analysis indicates the additive product to be 100% converted to the ester. The additive is soluble in hydrocarbon oil to the extent of greater than about 10 volume percent. A lubricating oil composition containing 10 volume percent of the inventive additive has a NLI Of 110 relative to a standard oil composition containing 10 volume percent of a commercially available lubricity additive which by definition has a NLI of 100. In addition, the oil composition containing the inventive additive exhibits thermal stability as good as that of the oil composition containing the commercial additive.

The additive of this invention may be prepared by condensing a monocarboxylic acid containing about 8 to carbons with a polyether-polyester polyol of the type disclosed in US. Pat. 3,455,886. While a preferred polyetherpolyester polyol prepared from glycerol, phthalic anhydride, and propylene oxide has been exemplified herein, it will be understood that polyether-polyester polyols within the scope of U8. Pat. 3,455,886 may in general be condensed with a suitable monocarboxylic acid to yield our detergency additive. The additive may be prepared by condensing the polyether-polyester polyol with, for example, S-methylheptanoic acid, Z-ethylhexanoic acid, 9-ethyldodecanoic acid, phenylstearic acid, l8-butyleicosoic acid, 8-ethyldecanoic acid, p-isostearylbenzoic acid, 4-isododecyl-l-cyclohexanoic acid, 4-(17-ethyloctadecyl)-l-naphthoic acid, 1-isododecyl-5-carboxycyclooctane, isostearic acid, and mixture thereof. The ratio of monocarboxylic acid to the polyether-polyester polyol is such as to convert about 85% to 100%, and preferably 100%, of the hydroxyl groups of the polyol to ester groups by condensation with the monocarboxylic acid.

The petroleum hydrocarbon compositions of our invention broadly comprise a major proportion of a petroleum hydrocarbon product and a minor proportion of the inventive additive. Generally, the petroleum hydrocarbon compositions contain about 1 to 20% by volume, and preferably about 3 to 15% by volume, of the additive of this invention. The additives of the instant invention are useful in petroleum hydrocarbon products generally, but it is contemplated that the additives will have their greatest utility in gasoline and in hydrocarbon engine oils, particularly in 2-cycle engine oils.

While our invention has been illustrated by various specific examples, it will be understood that the scope of our invention is not restricted thereto.

We claim:

1. A detergency additive for petroleum hydrocarbon products comprising the condensation product of a polyether-polyester polyol having 2 to about 12 hydroxyl groups and a monocarboxylic acid selected from the group consisting of aliphatic acids, aromatic acids having on the aromatic ring a branched aliphatic chain containing at least 12 carbons, and naphthenic acids having on the naphthenic ring a branched aliphatic chain containing at least 12 carbons, said monocarboxylic acid being free of ethylenic unsaturation, wherein at least about of the hydroxyl groups of said polyol are converted to ester groups by condensation with said monocarboxylic acid.

/ 2. The detergency additive of claim 1 wherein the polyether-polyester polyol is prepared by reacting an anhydride of a polycarboxylic acid with a polymerization starter compound containing at least 2 alcoholic hydroxyl groups to form a partial ester substantially free of unreacted anhydride, and thereafter reacting said partial ester with an excess, based on the amount of anhydride reacted, of a cyclic ether containing at least 1 heterocyclic ring comprising ethereal oxygen and at least 2 carbons.

3. The detergency additive of claim 2 wherein the ratio of equivalents of said anhydride to equivalents of said starter compound is from about 0.1 to about 2.0 and the amount of cyclic ether is from about 1.5 to about 14 equivalents per equivalent of said anhydride.

4. The detergency additive of claim 3 wherein the monocarboxylic acid contains about 8 to 30 carbons.

5. The detergency additive of claim 4 wherein the starter compound is glycerol, the polycarboxylic acid anhydride is phthalic anhydride, the cyclic ether is propylene oxide, and the polyether-polyester polyol has 3 hydroxyl groups and an equivalent weight of about 130.

6. The detergency additive of claim 5 wherein the monocarboxylic acid is an isoaliphatic acid containing about 12 to 24 carbons and about 85 to of the hydroxyl groups of said polyol are converted to ester groups by condensation with said isoaliphatic acid.

7. The detergency additive of claim 6 wherein the isoaliphatic acid is isostearic acid and about 100% of the hydroxyl groups of said polyol are converted to ester groups by condensation with said isostearic acid.

References Cited UNITED STATES PATENTS 3,455,886 7/1969' Versnel 26078.4 3,427,267 2/1969 Stieger et al. 260-22 3,382,217 5/1968 Case 260-784 JOSEPH L. SCHOFER, Primary Examiner I. KIGHT, Assistant Examiner US. Cl. X.R.

252-56 R; 260-75 T, 76, 78.4 E 

